نتایج جستجو برای: noble gas

تعداد نتایج: 252530  

2009
Hanna Tanskanen Zofia Mielke

Noble gases are mostly known as inert monatomic gases due to their limited reactivity with other elements. However, the first predictions of noble-gas compounds were suggested by Kossel in 1916, by von Antropoff in 1924, and by Pauling in 1930. It took many decades until the first noble-gas compound, XePtF6, was synthesized by Neil Bartlett in 1962. This was followed by gradual development of t...

2008
Tie Sun Chris M. Hall Maria Clara Castro Kyger C. Lohmann Patrick Goblet

[1] A key assumption for calculating paleotemperatures using noble gas concentrations in groundwater is that water equilibrates with standard air. However, if the unsaturated zone is depleted in O2, the noble gas partial pressures will be elevated, resulting in a bias of noble gas temperatures (NGTs) to low values. This oxygen depletion (OD) mechanism was used to explain low NGT values for a sh...

2005
Chris M. Hall Maria Clara Castro Kyger C. Lohmann Lin Ma

[1] Noble gas data from the Glacial Drift, the shallowest aquifer in southern Michigan confirm findings by Ma et al. (2004) that modern noble gas temperatures (NGTs) are systematically below the current mean annual air temperature (MAAT) which, in turn, is similar to the ground temperature of these recharge waters. By tracking noble gas concentrations as well as stable isotope ratios through an...

2012
Gisela Winckler Jeffrey P. Severinghaus

Noble gas analysis can be performed on two types of ice core samples. First, atmospheric air, trapped in bubbles in polar ice, can be extracted and analyzed for its noble gas composition. Variations in the isotopic and elemental composition of noble gases reveal changes in the composition of the paleoatmosphere or the impact of climate-related physical processes acting when the air was enclosed...

Journal: :European journal of mass spectrometry 2011
Felice Grandinetti

This review article surveys recent experimental and theoretical advances in the gas-phase ion chemistry of the noble gases. Covered issues include the interaction of the noble gases with metal and non-metal cations, the conceivable existence of covalent noble-gas anions, the occurrence of ion-molecule reactions involving singly-charged xenon cations, and the occurrence of bond-forming reactions...

2004
M. S. Brennwald F. Peeters D. M. Imboden S. Giralt R. Kipfer

[1] Lake sediment pore water has been proposed as a noble gas archive for paleoenvironmental reconstruction, but appropriate experimental techniques have not been available until recently. Here we present noble gas concentrations measured in the sediment pore water of Lake Issyk-Kul (Kyrgyzstan) which demonstrate for the first time the value of the sediment pore water archive for paleoclimate r...

2009
S. Matsuda H. Iio K. Bajo K. Nagao

Introduction: Chondrules are free from trapped noble gases [e.g., 1], which is attributed to complete degassing during the chondrule formation. However, Okazaki et al. [2] discovered the Ar-rich trapped noble gases in enstatite chondrite chondrules. The Ar-rich gases were formed via incomplete degassing (He and Ne depletion) of implanted solar gases during the chondrule formation [2]. Since sol...

Journal: :Ground water 2009
Bradley D Cey G Bryant Hudson Jean E Moran Bridget R Scanlon

Water table temperatures inferred from dissolved noble gas concentrations (noble gas temperatures, NGT) are useful as a quantitative proxy for air temperature change since the last glacial maximum. Despite their importance in paleoclimate research, few studies have investigated the relationship between NGT and actual recharge temperatures in field settings. This study presents dissolved noble g...

Journal: :Journal of magnetic resonance 2001
L Zhao A K Venkatesh M S Albert L P Panych

Some non-Fourier encoding methods such as wavelet and direct encoding use spatially localized bases. The spatial localization feature of these methods enables optimized encoding for improved spatial and temporal resolution during dynamically adaptive MR imaging. These spatially localized bases, however, have inherently reduced image signal-to-noise ratio compared with Fourier or Hadamad encodin...

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